Ultrafast Fluctuations of High Amplitude Electric Fields in Lipid Membranes,Journal of the American Chemical Society

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Ultrafast Fluctuations of High Amplitude Electric Fields in Lipid Membranes
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-03-22 , DOI: 10.1021/jacs.6b12412
Paul Stevenson _{1,

2} , Andrei Tokmakoff ₂

Affiliation

Understanding the electrostatics of lipid membranes at a molecular level has the potential to offer great insight into the mechanism of voltage-gated processes but has been challenging to study experimentally. In this study, we characterize the equilibrium electric field fluctuations at the interfacial region of lipid bilayers by using a combination of ultrafast time-resolved infrared spectroscopy, molecular dynamics (MD) simulations, and spectral modeling. By monitoring the dynamics of the ester carbonyl stretching vibration in hydrated phosphocholine lipid bilayers, we are able to measure a correlation function for the femtosecond and picosecond fluctuations in the local electric field of the membrane, estimating the standard deviation in these fluctuations as ∼10MV/cm. The addition of gramicidin D at a 1:20 mol ratio with DMPC results in the formation of protein-lipid hydrogen bonds, which alter the dynamics of the ester groups. Using MD simulations, we conclude that ultrafast local field fluctuations exist whether or not water interacts with the ester groups; however, water does accelerate the time-scale of these fluctuations.

中文翻译：

脂质膜中高振幅电场的超快波动

在分子水平上了解脂质膜的静电有可能为深入了解电压门控过程的机制提供巨大的洞察力，但实验研究一直具有挑战性。在这项研究中，我们结合使用超快时间分辨红外光谱、分子动力学 (MD) 模拟和光谱建模来表征脂质双层界面区域的平衡电场波动。通过监测水合磷酸胆碱脂质双层中酯羰基伸缩振动的动力学，我们能够测量膜局部电场中飞秒和皮秒波动的相关函数，估计这些波动的标准偏差为 ~10MV/厘米。在 1 处添加短杆菌肽 D：与 DMPC 的 20 摩尔比导致蛋白质-脂质氢键的形成，从而改变酯基的动力学。使用 MD 模拟，我们得出结论，无论水是否与酯基相互作用，都存在超快的局部场波动；然而，水确实加速了这些波动的时间尺度。

更新日期：2017-03-22

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